Cancer
Strive not to be a success, but rather to be of value.
~ Albert Einstein
Cancer is unregulated multiplication of some of the body's cells. Cancer occurs because one or more of the complex systems that control cell multiplication become damaged. Most often, cancer is the result of the DNA inside a cell becoming damaged (or "mutated") by environmental agents including radiation, viruses, and toxic chemicals. Because cancer cells reproduce uncontrollably, they rob normal cells of nutrients and space in which to grow. Eventually normal cells starve, their functions cease, and the organism dies.
Because organisms must live in the environment, cancer is inevitable. However, plants and animals have sophisticated mechanisms to detect and destroy cancer cells that arise within them. Sometimes cancers are too aggressive for the body's defenses and a cancer grows into a solid mass called a tumor. Sometimes cancer cells break away from their site or origin and spread to other parts of the body where they grow. The spread of cancer cells is called metastasis (Wikipedia on metastasis)
Some individuals are more vulnerable to certain types of cancer because a sensitive part of their DNA is prone to mutation. For example, some women have a part of their DNA that makes them prone to getting breast cancer. Very few types of cancer are related to cancer-prone DNA, however. Most cancers are caused by exposure of cells to cancer causing chemicals, such as those in cigarette smoke.
The general treatments of cancer are to remove cancer cells before they multiply and metastasize and/or kill the cancer cells with drugs and radiation.
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